Underground exploitation of fuel deposits



Feb. 21, 1950 D. DALIN UNDERGROUND EXPLOI'I'A'IIO}! 0F DEPOSITS FiledOct. 10, 1945 gu x3558? av 27 Balm 0 4m OP Patented Feb. 21, 1950UNDERGROUND EXPLOITATION 0F FUEL DEPOSITS David Dalin, Sodertalje,Sweden Application October 10, 1946, Serial No. 702,533 8 Claims. (Cl.2621) This invention relates to a method of burning and degassingsubterranean fuel deposits, and more particularly to a method of burningsuch fuel deposits without mining them, in order to obtain the productsof distillation thereof and to release and utilize their heat energy;

Underground deposits of such fuel minerals as shale and brown coal,having a high percentage of distillate products, are found in severallocations in the United States, and are widely distributed in otherparts of the world.

Heretofore it has been necessary, in order to obtain the volatileproducts of such deposits, to unearth them and subject them to drydistillation in large, specially constructed retorts.

Although this method is efficient in that it recovers a high percentageof the distillates present in the minerals, it nevertheless requiresthat the fuel be mined and specially handled.

It is, therefore, an object of this invention to provide a. method ofrecovering the distillate products of subterranean fuel deposits withoutthe necessity of unearthing such deposits or constructing specialapparatus for their distillation.

A further object of this invention resides in the provision of a methodof releasing and utilizing the heat energy of underground fuel depositswithout mining them.

In this connection it is another object of this invention to provide a.steam generating unit adapted to be removably inserted into selectedportions of a bed of burning subterranean fuel deposits and to be movedfrom place to place as combustion proceeds so as to utilize the heatenergy of the fuel to the best advantage for the generation of steam.

Still another object of this invention resides in the cheap andconvenient method which it provides for releasing the heat energy anddistillate products of underground fuel deposits.

With the above and other objects in view which will appear as thedescription proceeds, this invention resides in the novel method ashereinafter described and more particularly defined by the appendedclaims, it being understood that such changes in the precise embodimentof the hereindisclosed invention may be made as come within the scope'ofthe claims.

The accompanying drawing illustrates one complete example of thephysical embodiment of the invention constructed in accordance with thebest mode so far devised for the practical application of the principlesthereof, and in which:

through an underground fuel deposit and illustrates one adaptation ofthis invention.

Referring now more particularly to the accompanying drawing, the numerall designates generally an underground deposit of lignitic fuellying'between a noncombustible layer 2 of soil and rock which extends tothe earth's surface and a layer of bed rock 3 underlying the fuel bed.

The first step in the application of the method of this invention is todrill a series of spaced apart holes 4 into the fuel deposit. Ordinarilythese holes would be drilled from the surface of the earth though theymight be drilled from the terial in quantities sufllcient to maintainsatis- The single figure represents a sectional view 55 factorycombustion.

Preferably, though not necessarily, the air pumped into the fuel depositis preheated in a suitable preheater 6. The preheating of the airfacilitates the ignition and combustion 'of the fuel.

Tubes or other suitable ducts l are inserted into the holes in thecombustion area 8, and a heat absorbing medium such as water or awatersteam emulsion is continuously forced through them by means of a,pump 9. By regulating the flow of the heat absorbing medium, thetemperature of combustion of the fuel bed in the combustion area 8 maybe regulated so as to keep it below the sintering temperature of thefuel.

The heat energy of the medium so heated may be collected at some centralpoint III as for instance a common steam dome. This enables the heatenergy absorbed from the burning fuel bed 8 to be put to useful purposesin. any known manner. I

The tubes or ducts I are, of course, removable from the holes into whichthey are inserted to enable the same to be moved from place to place asrequired to most effectively utilize the heat of the burning fuel, andsimilarly the collecting unit I0 should be movable.

In the zone 'I I surrounding the combustion area or adjacent thereto,distillation of the fuel material occurs as a result of the heating ofthe material in that zone by combustion of the fuel which is alreadyburning. The .distillates so re- 3 leased are recovered by means ofpipes I2 connected to the mouths of holes in the zone of distillation,which lead to a suitable accumulator I3 in which the distillates may bestored to be available for refinement or other desired use.

As the combustion process continues, the initially ignited area 8 burnsthrough, and the combustion process spreads to the residual coke l Ileft in the wake of distillation.

Dry distillation now occurs in a new zone surrounding or adjacent to thezone ll of original distillation, as a result of the combustion of theresidual coke, and the distillate products in the new zone ofdistillation are recovered in the manner described. Thus the combustionand distillation processes will spread outward, from the point ofinitial ignition as a center, with distillation occurring in the zone ofunburnedfuel in the neighborhood of the combustion area. As distillationis completed, combustion occurs in the residual coke.

To sustain combustion and maintain the distillation process, it is onlynecessary that compressed air be continuously forced into the neighborhood of the combustion area. If desired some of the distillation gasmay be bled off from the accumulator l3 by a valved duct l4 which leadsto the inlet of the pump 5. In this manner a readily combustible gaseousfuel mixture will be pumped into the fuel bed.

As the process advances through the fuel bed it is necessary from timeto time to move the air supply 6 and the tubes 1 through which the heatabsorbing medium flows, together with the pipes I2 and other means forcollecting the distillate products.

The smoke and other waste products of combustion rising from the holes 4which lead to the combustion zone are collected in hoods [5 appropiatelyplaced over these holes, and ducts l6 carry these waste gases to a stackor chimney l'l. Preferably an exhaust fan I8 is provided to morepositively effect the withdrawal of the smoke and waste gases. Like allthe other apparatus, the hoods l5 are movable and the ducts l6 areadjustable to enable necessary shifting of the hoods with little or noneed for moving the stack or chimney.

Since sintering of the underground fuel deposit would seriouslyinterfere with its proper combustion, it is necessary that thetemperature of combustion be kept below that at which sintering occursin the particular fuel. This is accomplished by regulating the flow ofthe heat absorbing medium through the tubes or ducts l which, however,at all times serves the additional purpose of recovering the heat energyreleased by the burning fuel.

From the foregoing description, taken in connection with theaccompanying drawing, it will be readily apparent that this inventionprovides a method for burning and degassing subterranean fuel depositsin order to release and recover from them their distillate products andheat energy without necessitating digging them out of the earth.

What I claim as my invention is:

1. The method of degassing and burning a subterranean fuel deposit whichcomprises the steps of drilling a plurality of spaced apart holes intothe fuel deposit from the surface of the earth; igniting the fueldeposit at one point; forcing combustion supporting fluid into the fueldeposit through at least one of the holes in order to sustain combustionof the fuel deposit; inserting tubes into the holes in the area ofcombustion; circulating a cooling medium through said tubes to therebyregulate the heat of combustion of the burning fuel bed to keep it belowthe sintering point of the fuel; and collecting from the mouths of holesin a zone adjacent to the combustion area the distillation productsreleased by the heat of combustion.

2. The method of obtaining the heat energy and distillates of anunderground fuel deposit which comprises the steps of: drilling aplurality of spaced apart holes from the surface of the earth into thefuel deposit; igniting the deposit at one point; continuously forcingcombustion supporting fluid into the deposit near the point ofcombustion to sustain combustion; inserting tubes into holes in thedeposit in the area of combustlon; passing a cooling medium through saidtubes whereby the temperature of combustion of the burning fuel will bekept below the sintering point of the fuel; collecting and utilizing theheat energy absorbed by the cooling medium; and

collecting from the mouths of holes in a zone ad- I circulating a heattransfer medium through said tubes; and collecting said heat transfermedium and utilizing the heat energy absorbed thereby.

4. The method of releasing and utilizing the heat energy of subterraneanfuel deposits which comprises the steps of: boring a plurality of spacedapart holes from the surface of the earth into the fuel deposit;igniting the fuel deposit at one point: forcing combustion supportingfluid through one of said holes into the fuel deposit to sustaincombustion thereof; inserting tubes in to holes in the area ofcombustion; passing a heat transfer medium through said tubes in suchquantitles as to regulate the heat of combustion of the fuel in order tokeep it below the sintering point thereof; and collecting the heattransfer medium and utilizing the heat absorbed by it.

5. The method of releasing and utilizing the heat energy of asubterranean fuel deposit which comprises the steps of: boring aplurality of spaced apart holes into the fuel deposit; igniting the fueldeposit; forcing combustion supporting fluid into the fuel deposit tosustain combustion thereof; inserting steam generating coils into theholes in the area of combustion; positively circulating a water steamemulsion from a common steam accumulator through all of the coils andback to the accumulator to thus carry off the heat of combustion andconvert it into steam energy; and moving the steam generating coils fromburned out areas into freshly burning areas as combustion of the fueldeposit proceeds.

6. The method of releasing and utilizing the heat energy of asubterranean fuel deposit which comprises the steps of: boring aplurality of spaced apart holes into the fuel deposit; igniting the fueldeposit; forcing combustion supporting fluid into the fuel deposit tosustain combustion thereof; inserting steam generating coils into theholes in the area of combustion; positively circulating a water steamemulsion from a common steam accumulator through all of the coils and 5back to the accumulator to thus carry oi! the heat of combustion andconvert it into steam energy: collecting the smoke and waste products ofcombustion issuing from the holes which lead to the burning portions ofthe fuel deposit; and con-- and wasteproducts to veying the collectedsmoke a stack.

7. The method of exploiting an underground fuel deposit which comprises:igniting the fuel deposit; forcing combustion supporting fluid into thefuel deposit to sustain the combustion thereof inserting heat exchangeducts into the fuel de posit in the area of combustion; circulating aheat exchange medium through said ducts to thereby maintain thetemperature of combustion of the fuel below its sintering point; andcollecting the heat exchange medium so circulated and utilizing the heatenergy absorbed by it.

8. The method of exploiting an underground fuel deposit which comprises:forming a plurality of holes into the deposit; igniting the deposit;forcing combustion supporting fluid under pressure into the fuel depositthrough at least one of said holes to sustain combustion; inserting heatexchange ducts into said holes in the area of combustion; circulatingheat exchange medium 6 through said ducts; regulating the flow of saidheat exchange medium through said ducts to thereby control thetemperature of combustion of the fuel; collecting said heat exchangemedium to utilize the heat absorbed by it; and collecting from the mouthof a hole in a zone adjacent to the combustion area the products ofdistillation released by the heat of combustion.

DAVID DALIN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,913,395 Karrick June 13, 1933FOREIGN PATENTS Number Country Date 200,423 Germany July 17, 1908 OTHERREFERENCES American Gas Journal, pp. 28 and 29, January 1944.

